If you have multiple accounts, you can compose messages in Gmail and have them appear to be sent from your other email account. If you already use a custom From address in Gmail, you don't have to do any extra set up on your iPhone or iPad.

Open the Gmail app.

Touch Compose .

Touch From and choose one of your addresses.

Set up a new address

If you don't see "From" while composing, you need to change your Gmail settings on a computer so you can send mail as that address: